1. Field of the Invention
This invention relates to a process for chlorinating and dehydrochlorinating certain organic compounds and, in particular, a process for using a phosphorus complex, e.g., phenyltrichlorophosphonium hexachlorophosphate as a reactant.
2. Related Information
The phosphorus complex useful in the process of this invention is exemplified by the compound phenyltrichlorophosphonium hexachlorophosphate. This compound is known in the art and has heretofore been used in the preparation of certain phosphorus-containing compounds.
The article entitled "Reaction of Phosphorus Pentachloride With Unsaturated Hydrocarbons" by G. K. Fedorova et al., Zhur. Obshchei. Khim. 30 4044 (1960), reported the reaction of styrene with phosphorus pentachloride to form a colorless complex with the structure EQU C.sub.6 H.sub.5 CH.dbd.CHP.sup..sym. Cl.sub.3 P.sup..crclbar. Cl.sub.6.
This reference further disclosed that styrylphosphonous dichloride is formed when the complex is reacted with SO.sub.2. With styrene, the complex forms styrylphosphorus tetrachloride, and on reduction with red phosphorus, the complex is converted into styryldichlorophosphine. However, this reference does not disclose the unique processes of this invention.
In the article entitled "Tetrachloro-(m- and p-nitrophenyl) Phosphoranes" by I. N. Zhmurova et al., Org. Phos. Comp. Ref., 705, Vol. 3, Monatsh. 70, 1-19 (1937), the reaction disclosed in the previous reference was cited for preparing a phosphorus complex. This reference disclosed the treatment of EQU m- and p--NO.sub.2 C.sub.6 H.sub.4 P.sup..sym. Cl.sub.3 P.sup..crclbar. Cl.sub.6
with red phosphorus at a molar ratio of 3:2 to obtain tetrachloro-(nitrophenyl)phosphoranes. Again, this reference does not disclose the unique processes of this invention.
U.S. Pat. No. 4,634,771, Shim et al., Jan. 6, 1987, disclosed the reaction of carboxylic acid groups on aromatic ring compounds with phenylphosphonous dichloride, chlorine, and phosphorus trichloride to convert the carboxylic acid groups to trichloromethyl groups. This reference distinguished the use of phosphorus pentachloride and suggested that phosphorus pentachloride is specific for the conversion of a carboxylic acid group adjacent, or alpha, to the hetero-atom of an N-heteroaromatic (N=nitrogen) compound. However, this reference did not disclose the use of the phosphorus complex exemplified by phenyltrichlorophosphonium hexachlorophosphate that is used in the process of this invention.
U.S. Pat. No. 4,419,514, McKendry et al., Dec. 6, 1983, disclosed a method for converting carboxylic acid groups to trichloromethyl groups which comprises contacting a compound containing a carboxylic acid group with phenylphosphonic dichloride and phosphorus pentachloride at a specified molar ratio for a time and at a temperature sufficient to carry out the conversion of a carboxylic acid group to a trichloromethyl group. However, this reference does not disclose the use of a phosphorus complex as the chlorinating agent. In fact, this reference teaches that it is helpful to allow the carboxylic acid compound and the phenylphosphonic dichloride compound to react for a period of time (until HCl evolution ceased) before adding the phosphorus pentachloride.
U.S. Pat. No. 4,167,525, Kataoka et al., Sept. 11, 1979, disclosed the preparation of aromatic acyl chlorides by reacting an aromatic carboxylic acid, phosphorus trichloride, and chlorine to produce phosphorus pentachloride in situ which is then treated with either water or certain phosphorus compounds to convert the phosphorus pentachloride into phosphorus oxychloride. The resulting reaction mixture is then distilled to obtain phosphorus oxychloride and, successively, the desired aromatic acyl chloride. The process of this reference improves prior known processes by allowing the preparation of the aromatic acyl chloride without causing blocking of the distillation equipment by phosphorus pentachloride and without formation of troublesome by-products. However, this reference does not disclose the use of a phosphorus complex as disclosed in the process of this invention.